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Message-Id: <1498665337-28845-4-git-send-email-aleksandar.markovic@rt-rk.com>
Date: Wed, 28 Jun 2017 17:55:30 +0200
From: Aleksandar Markovic <aleksandar.markovic@...rk.com>
To: linux-mips@...ux-mips.org
Cc: Goran Ferenc <goran.ferenc@...tec.com>,
Miodrag Dinic <miodrag.dinic@...tec.com>,
Aleksandar Markovic <aleksandar.markovic@...tec.com>,
Douglas Leung <douglas.leung@...tec.com>,
James Hogan <james.hogan@...tec.com>,
linux-kernel@...r.kernel.org, Paul Burton <paul.burton@...tec.com>,
Petar Jovanovic <petar.jovanovic@...tec.com>,
Raghu Gandham <raghu.gandham@...tec.com>,
Ralf Baechle <ralf@...ux-mips.org>
Subject: [PATCH v2 3/4] MIPS: VDSO: Add implementation of gettimeofday() fallback
From: Goran Ferenc <goran.ferenc@...tec.com>
This patch adds gettimeofday_fallback() function that wraps assembly
invocation of gettimeofday() syscall using __NR_gettimeofday.
This function is used if pure VDSO implementation gettimeofday()
does not succeed for any reason. Its imeplementation is enclosed in
"#ifdef CONFIG_MIPS_CLOCK_VSYSCALL" to be in sync with the similar
arrangement for __vdso_gettimeofday().
If syscall invocation via __NR_gettimeofday fails, register a3 will
be set. So, after the syscall, register a3 is tested and the return
valuem is negated if it's set.
Signed-off-by: Goran Ferenc <goran.ferenc@...tec.com>
Signed-off-by: Miodrag Dinic <miodrag.dinic@...tec.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@...tec.com>
---
arch/mips/vdso/gettimeofday.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/arch/mips/vdso/gettimeofday.c b/arch/mips/vdso/gettimeofday.c
index 5f63375..23305bf 100644
--- a/arch/mips/vdso/gettimeofday.c
+++ b/arch/mips/vdso/gettimeofday.c
@@ -20,6 +20,28 @@
#include <asm/unistd.h>
#include <asm/vdso.h>
+#ifdef CONFIG_MIPS_CLOCK_VSYSCALL
+
+static __always_inline long gettimeofday_fallback(struct timeval *_tv,
+ struct timezone *_tz)
+{
+ register struct timezone *tz asm("a1") = _tz;
+ register struct timeval *tv asm("a0") = _tv;
+ register long ret asm("v0");
+ register long nr asm("v0") = __NR_gettimeofday;
+ register long error asm("a3");
+
+ asm volatile(
+ " syscall\n"
+ : "=r" (ret), "=r" (error)
+ : "r" (tv), "r" (tz), "r" (nr)
+ : "memory");
+
+ return error ? -ret : ret;
+}
+
+#endif
+
static __always_inline long clock_gettime_fallback(clockid_t _clkid,
struct timespec *_ts)
{
@@ -205,7 +227,7 @@ int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
ret = do_realtime(&ts, data);
if (ret)
- return ret;
+ return gettimeofday_fallback(tv, tz);
if (tv) {
tv->tv_sec = ts.tv_sec;
--
2.7.4
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